Configuration & env flags

Environment variables

Variable	Default	Effect
IFX_BUFFERED_READER	1	Enable connection-scoped read buffer (Phase 39). Set to 0 to disable.
IFX_DEBUG_WIRE	unset	When set to a truthy value, log wire-level PDU framing to stderr. Verbose; for debugging only.
IFX_PROTOCOL_TRACE	unset	When set to a path, write annotated wire captures to the file.
IFX_DISABLE_PIPELINE	unset	Disables pipelined executemany (Phase 33). Use only to A/B-measure.
INFORMIXSERVER	—	Read by connect() if server= is not provided.

Environment variables are read at connection construction. Changing them at runtime doesn’t affect existing connections.

Connection arguments

Full keyword list for informix_db.connect():

Arg	Type	Default	Notes
host	str	required	TCP host.
port	int	9088	TCP port. 9089 is the typical TLS listener.
user	str	required
password	str	required
database	str | None	required	None logs in without selecting a DB.
server	str	required	DBSERVERNAME, not hostname.
autocommit	bool	False
connect_timeout	float | None	None	TCP+login timeout.
read_timeout	float | None	None	Per-read timeout.
keepalive	bool	False	SO_KEEPALIVE.
client_locale	str	"en_US.8859-1"	See SQL ↔ Python types for codec mapping.
env	dict[str, str] | None	None	Server-side session env.
tls	bool | ssl.SSLContext	False	See Connect with TLS.

Pool tunables

Arg	Default	Effect
min_size	1	Connections to pre-warm at create time.
max_size	10	Hard cap.
acquire_timeout	30.0	Raise PoolTimeout after this many seconds.
max_idle	600.0	Close connections idle longer than this (seconds).
health_check	True	Validate idle connections before returning from the pool.

All other connection arguments are forwarded to each pool-created connection.

Server-side session env

The env={} parameter of connect() sets server session variables sent in the login PDU:

informix_db.connect(
    ...,
    env={
        "OPT_GOAL": "-1",      # optimize for first-row return
        "OPTOFC": "1",         # auto-free cursors at fetch-close
        "IFX_AUTOFREE": "1",
    },
)

CLIENT_LOCALE is set automatically from client_locale= — don’t put it in env=.